1. Field of the Invention
This invention relates generally to refrigerator air circulation systems, and more particularly, an improved air circulation system for controlling an air outlet baffle.
2. Description of Background Art
Conventional dual compartment refrigerators of the forced air circulation type utilize a single evaporator and an evaporator fan for cooling a freezer compartment thereof. The freezer compartment is coupled by means of inlet and outlet passages through a divider wall to a fresh food compartment. A controllable baffle has been located within the fresh food compartment air inlet passage, which is operated by a control circuit to control the passage of refrigerated air into the fresh food compartment. Such an arrangement is shown in Janke, U.S. Pat. No. 4,682,474, assigned to the assignee of the present invention.
With such a conventional refrigerator, when the refrigeration unit is operating the evaporator fan forces air flow across the evaporator coils and out the top freezer into a scoop which directs air to the fresh food compartment, past the baffle. The fan flow overcomes natural convective flow caused by air density difference. Resultantly, with the fan on, air enters at the top, circulating within the fresh food compartment, and returns out of the bottom, back to the freezer.
During a conventional automatic defrost cycle, moisture can accumulate on the baffle. Once the defrost cycle is complete, the subsequent unit cycle time is of greater length since the cabinet must overcome the heat produced by the defrost heater. The colder air from the evaporator coils can cause moisture on the baffle to freeze. The resulting ice prevents free movement of the baffle resulting in over-cooling of the fresh food compartment.
Additionally, when the evaporator fan is off, air flow is controlled by natural convection. The colder and denser freezer air flows from the freezer bottom in a reverse direction through the compartment air outlet into the bottom of the fresh food compartment. With high ambient temperatures, where unit off time is short, such periods of uncontrolled back flow are short in duration so that performance is not hampered. However, with lower ambient temperatures, unit off time tends to be greater in duration resulting in the periods of uncontrolled back flow being longer. These long periods of back flow can result in the bottom portion of the fresh food compartment being overcooled causing freezing of articles therein.
The present invention overcomes the above problems with prior refrigerator air circulation systems, in a novel and simple manner.